The Dell PowerStore back-end SAS cabling topology utilizes a redundant loop configuration to ensure high availability and performance. When cabling a single expansion enclosure, it functions as both the "first" and "last" enclosure in the chain.

According to the Dell PowerStore Installation and Service Guide:

1. Outbound Connection (Start of Loop): SAS Port B on the base nodes connects to the input (Port A) of the first expansion enclosure LCCs.

• Node A SAS B $\rightarrow$ LCC A Port A.
• Node B SAS B $\rightarrow$ LCC B Port A.

1. Return Connection (End of Loop): SAS Port A on the base nodes connects to the output (Port B) of the last expansion enclosure LCCs to close the loop. Note that this connection is crossed for redundancy.

• Node A SAS A $\rightarrow$ LCC B Port B.
• Node B SAS A $\rightarrow$ LCC A Port B.

Dell Technologies, "Dell PowerStore Installation and Service Guide (Models 1000-9200)," Section: Cable the base enclosure to the expansion enclosure.

Quote: "Cable SAS port B from each node on the base enclosure to the link control card (LCC) on the first expansion enclosure in the stack: Connect node A, SAS port B to LCC A, port A... Connect node B, SAS port B to LCC B, port A."

Quote: "Cable SAS port A from each node on the base enclosure to the LCCs on the last expansion enclosure in the stack: Connect node A, SAS port A to LCC B, port B... Connect node B, SAS port A to LCC A, port B."

Dell Technologies, "PowerStore Hardware Information Guide," Chapter: Back-end Cabling.

Dell Technologies, PowerStore Information Hub, "Cabling diagrams for PowerStore T and PowerStore X models."